'r' (reduce lost types) is a subroutine in 'R' (Reduce).
This 'r' only kicks in when an OTFT can be reduced, and when there's no more FTE under it.
Without the 'r', these empty OTFTs will remain in the model as reference to the object types which were present in the conceptual model, yet have not fact expression themselves.

Closing automatically, stayed too long in resolved state. Feel free to re-open with additional information if you think the issue is not resolved.